MDKSA-2005:145

Problem description

A number of vulnerabilities were discovered in OpenVPN that were fixed
in the 2.0.1 release:
A DoS attack against the server when run with "verb 0" and without
"tls-auth" when a client connection to the server fails certificate
verification, the OpenSSL error queue is not properly flushed. This
could result in another unrelated client instance on the server seeing
the error and responding to it, resulting in a disconnection of the
unrelated client (CAN-2005-2531).
A DoS attack against the server by an authenticated client that sends
a packet which fails to decrypt on the server, the OpenSSL error queue
was not properly flushed. This could result in another unrelated
client instance on the server seeing the error and responding to it,
resulting in a disconnection of the unrelated client (CAN-2005-2532).
A DoS attack against the server by an authenticated client is possible
in "dev tap" ethernet bridging mode where a malicious client could
theoretically flood the server with packets appearing to come from
hundreds of thousands of different MAC addresses, resulting in the
OpenVPN process exhausting system virtual memory (CAN-2005-2533).
If two or more client machines tried to connect to the server at the
same time via TCP, using the same client certificate, a race condition
could crash the server if --duplicate-cn is not enabled on the server
(CAN-2005-2534).
This update provides OpenVPN 2.0.1 which corrects these issues as well
as a number of other bugs.